Department of Materials and London Centre for Nanotechnology, Imperial College London , Exhibition Road, London SW7 2AZ, U.K.
Environ Sci Technol. 2013 Oct 1;47(19):11232-40. doi: 10.1021/es403377p. Epub 2013 Sep 18.
The growing use of silver nanoparticles (AgNPs) in consumer products has raised concerns about their potential impact on the environment and human health. Whether AgNPs dissolve and release Ag(+) ions, or coarsen to form large aggregates, is critical in determining their potential toxicity. In this work, the stability of AgNPs in dipalmitoylphosphatidylcholine (DPPC), the major component of pulmonary surfactant, was investigated as a function of pH. Spherical, citrate-capped AgNPs with average diameters of 14 ± 1.6 nm (n = 200) were prepared by a chemical bath reduction. The kinetics of Ag(+) ion release was strongly pH-dependent. After 14 days of incubation in sodium perchlorate (NaClO4) or perchloric acid (HClO4) solutions, the total fraction of AgNPs dissolved varied from ∼10% at pH 3, to ∼2% at pH 5, with negligible dissolution at pH 7. A decrease in pH from 7 to 3 also promoted particle aggregation and coarsening. DPPC (100 mg·L(-1)) delayed the release of Ag(+) ions, but did not significantly alter the total amount of Ag(+) released after two weeks. In addition, DPPC improved the dispersion of the AgNPs and inhibited aggregation and coarsening. TEM images revealed that the AgNPs were coated with a DPPC layer serving as a semipermeable layer. Hence, lung lining fluid, particularly DPPC, can modify the aggregation state and kinetics of Ag(+) ion release of inhaled AgNPs in the lung. These observations have important implications for predicting the potential reactivity of AgNPs in the lung and the environment.
纳米银颗粒（AgNPs）在消费产品中的应用日益广泛，这引起了人们对其潜在环境和健康影响的关注。AgNPs 是否溶解并释放出 Ag(+)离子，或者粗化为大的聚集物，对于确定其潜在毒性至关重要。在这项工作中，研究了 AgNPs 在肺表面活性剂主要成分二棕榈酰磷脂酰胆碱（DPPC）中的稳定性随 pH 值的变化。采用化学浴还原法制备了平均直径为 14 ± 1.6 nm（n = 200）的球形、柠檬酸封端的 AgNPs。Ag(+)离子释放的动力学强烈依赖于 pH 值。在高氯酸钠（NaClO4）或高氯酸（HClO4）溶液中孵育 14 天后，AgNPs 的总溶解分数从 pH 3 时的约 10%变化到 pH 5 时的约 2%，而在 pH 7 时几乎没有溶解。pH 值从 7 降低到 3 也促进了颗粒的聚集和粗化。DPPC（100mg·L(-1)）延迟了 Ag(+)离子的释放，但在两周后并没有显著改变释放的总 Ag(+)量。此外，DPPC 改善了 AgNPs 的分散性，并抑制了聚集和粗化。TEM 图像显示，AgNPs 被 DPPC 层覆盖，形成半透膜。因此，肺衬液，特别是 DPPC，可以改变吸入 AgNPs 在肺部的聚集状态和 Ag(+)离子释放动力学。这些观察结果对预测 AgNPs 在肺部和环境中的潜在反应性具有重要意义。
